The Jewish leaders who brought the woman to Jesus also forgot to bring something else - the man.
The law (Leviticus 20:10) states, "If a man commits adultery with another man’s wife—with the wife of his neighbor—both the adulterer and the adulteress are to be put to death." Jesus' response to the woman is just as much a rebuke of the "leaders" who perverted the law and allowed the man to escape punishment. Leviticus 20 lists a range of sexual sins outside of monogamous heterosexual marriage. Jesus does not change the law, but expresses this greater law, "Do I take any pleasure in the death of the wicked? declares the Sovereign Lord. Rather, am I not pleased when they turn from their ways and live?" (Ezekiel 18:23).